Geochemical characterization of metaultramafic and metamafic rocks from Pajeú-Paraiba Belt - Northeast Brazil

Abstract

Concordant lenses of high pressure metaultramafic and metamafic rocks are positioned in Paleoproterozoic migmatites and orthogneisses of the Pajeú-Paraíba belt, Borborema Province, northeast Brazil. The geochemical signature of theses eclogites facies rocks points to a tholeiitic basaltic composition related to an island arc evolution. They are probably associated with a enriched mantle source underlying a subduction zone. This mantelic source was melted and further underwent in-situ differentiation, producing as high-MgO as high-FeO-TiO2 rocks. Cumulatic pyroxenites could be residual product of this process. The high-FeO-TiO2 group seems to represent more differentiated member submits to crustal contamination event. Reported positive and negative gravimetric anomalies in these metaultramafic and metamafic rocks occurrence area suggest the presence of possible NE-SW to E-W continental collision zone in the Borborema Province.